my 20 yr old child drives a truck registered to me in Texas. if she gets in an accident am i liable? she has her own insurance

What you are describing is a claim of negligent entrustment.  It makes no difference who insures the vehicle.  Negligent entrustment is a claim against the person who owns the vehicle.  My recommendation would be to either title the vehicle in you daughter's name only or, at least, add her name to the title.